A horoscope is an astrological chart or diagram representing the positions of the Sun, Moon, planets, astrological aspects, and sensitive angles at the time of an event, such as the moment of a person's birth. The word horoscope is derived from Greek words hõra and scopos meaning "time" "observer" (horoskopos, pl. horoskopoi, or "marker(s) of the hour.") Other commonly used names for the horoscope in English include "Natal Chart" astrological chart, astro-chart, celestial map, sky-map, star-chart, cosmogram, vitasphere, radical chart, radix, chart wheel, or simply chart. It is used as a method of divination regarding events relating to the point in time it represents, and it forms the basis of the horoscopic traditions of astrology.

In common usage, horoscope often refers to an astrologer's interpretation, usually based on a system of Solar Sun sign astrology;Based strictly on the position of the Sun at the Time of Birth, or on the calendar significance of an event, as in Chinese astrology. In particular, many newspapers and magazines carry predictive columns based on celestial influences in relation to the zodiacal placement of the Sun on the Month of birth, Cusp(2 days before or after any particular sign, an overlap), or decante(the month divided into 3 ten day periods) of the person month of birth, identifying the individual's Sun sign or "star sign" based on the tropical zodiac.[1]

No scientific studies have shown support for the accuracy of horoscopes, and the methods used to make interpretations are generally considered pseudo-scientific.[2] In modern scientific framework no known interaction exists that could be responsible for the transmission of the alleged influence between a person and the position of stars in the sky at the moment of birth. Besides, all tests done so far, keeping strict methods to include a control group and proper blinding between experimenters and subjects have shown no effect beyond pure chance. Further, some psychological tests have shown that it is possible to construct personality descriptions and foretelling generic enough to satisfy most members of a large audience simultaneously. This is usually referred to as the Forer or Barnum effect.

The horoscope serves as a stylized map of the heavens over a specific location at a particular moment in time. In most applications the perspective is geocentric (heliocentric astrology being one exception). The positions of the actual planets (including Sun and Moon) are placed in the chart, along with those of purely calculated factors such as the lunar nodes, the house cusps including the midheaven and the ascendant, zodiac signs, fixed stars and the lots. Angular relationships between the planets themselves and other points, called aspects, are typically determined. The emphasis and interpretation of these factors varies with tradition.

The Sanskrit term for horo is Hora (होरा).Horo -Scope is hora - shastra( होरा -शास्त्र ). The word Latinhoroscopus, ultimately from Greekὡρόσκοπος "nativity, horoscope", literally "observer of the hour [of birth]", from ὥρα "time, hour" and σκόπος "observer, watcher". In Middle English texts from the 11th century, the word appears in the Latin form, and is anglicized to horoscope in Early Modern English. The noun horoscopy for "casting of horoscopes" has been in use since the 17th century (OED). In Greek, ὡρόσκοπος in the sense of "ascendant" and ὡροσκοπία "observation of the ascendant" is in use since Ptolemy (Tetrabiblos 33, 75).

The native is the subject of the event (a birth, for example) being charted at a particular time and place, and is considered to be at the centre of the celestial sphere.

The celestial sphere is an imaginary sphere onto which the zodiac, constellations and planets are projected.

The plane of the equator is the plane of the Earth's equator projected into space.

The plane of the ecliptic is defined by the orbits of the earth and the sun. For practical purposes the plane of the equator and the plane of the ecliptic maintain a constant inclination to each other of approximately 23.5°.

The plane of the horizon is centred on the native, and is tangential to the earth at that point. In a sphere whose radius is infinitely large, this plane may be treated as nearly equivalent to the parallel plane with its centre at the Earth's center. This greatly simplifies the geometry of the horoscope, but does not take into account that the native is in motion. Some writers on astrology have thus considered the effects of parallax, but most would agree that (apart from that of the moon) they are relatively minor.[citation needed]

The ascendant is the easternmost or sunrise point where the ecliptic and horizon intersect; the ascendant and the midheaven are considered the most important angles in the horoscope by the vast majority of astrologers. In most systems of house division, the ascendant is the cusp of the 1st house and the midheaven is the cusp of the 10th house. The placement of the planetary ruler of the ascendant, called the chart ruler is also considered to be significant. The point in the west diametrically opposing the ascendant is called the descendant, normally the cusp of the 7th house; and the point opposing the M.C. is the cusp of the 4th house, the northernmost point of the chart, called the imum coeli or I.C.

In creating a horoscope the ascendant is traditionally placed at the "nine o'clock" position on the left-hand side of the chart wheel (though traditional rectangular chart formats need not follow this convention). During the course of a day, because of the Earth's rotation, the entire circle of the ecliptic will pass through the ascendant and will be advanced by about 1°. This movement provides us with the term rising sign, which is the sign of the zodiac rising over the eastern horizon at the moment of birth. The point on the ecliptic that is furthest above the plane of the horizon at the time is called the Midheaven, or medium coeli (M.C.), placed at the "twelve o'clock position" effectively where the Sun would be if the birth time was midday.

The zodiac, or "circle of animals" is a zone or belt n space projected onto the celestial sphere through which, from our viewpoint, the planets move. A symbolic geometric construction around 15 to 18 degrees wide, it is divided into 12 signs, each of 30 degrees longitude (making 360 degrees in all), with the ecliptic, the apparent path of the Sun, as its middle line. The tropical zodiac used by most Western astrologers has its beginning at the exact moment that the Sun crosses the celestial equator and enters the zodiacal sign of Aries. Some Western astrologers use the sidereal zodiac favoured by Indian ("jyotish") astrologers, which is based more closely on actual positions of constellations in the heavens, as opposed to the tropical zodiac, which is a moveable format based on the seasons.

The tropical zodiac defines the vernal point (the first day of spring in the northern hemisphere) as the first degree of Aries, but the sidereal zodiac allows it to precess. Many people are confused regarding the difference between the sidereal zodiac and the tropical zodiac signs. Because of a "wobble" in the Earth's axis of rotation over a period of about 26,000 years (often called a "great year"), the rate at which the vernal equinox precesses in the heavens is approximately 0 deg, 0 min, 50.23 seconds a year, drifting by one degree every 72 years. Precession of the equinoxes thus occurs at a rate of roughly 5 arc minutes of a degree every 6 years. The tropical signs relate to the seasons and not the stars. Here is an example: a person born on, say August 28, 2002 would come to understand that his/her Sun sign was in Virgo according to western astrology (conventional Sun sign dates August 23, to September 22, of every year), but Sun on that same calendar date of the year 2002 was in the constellation Leo (where it had been since August 10, 2002 and would remain until September 15, when it would then finally cross into Virgo).[3]

It is worth pointing out that the sidereal signs and the tropical signs are both geometrical conventions of 30° each, whereas the zodiacal constellations are pictorial representations of mythological figures projected onto the celestial sphere based on patterns of visible star groupings, none of which occupy precisely 30° of the ecliptic. So constellations and signs are not the same, although for historical reasons they might have the same names.[4]

It is also worth noting that some astrologers don't use the signs of the zodiac at all, focusing more instead on the astrological aspects and other features of the horoscope.

The sun sign is the sign of the zodiac in which the sun is located for the native. This is the single astrological fact familiar to most people. If an event occurs at sunrise the ascendant and sun sign will be the same; other rising signs can then be estimated at approximately two-hour intervals from there.

A cusp is the boundary between two signs or houses. For some the cusp includes a small portion of the two signs or houses under consideration.

The houses are a series of twelve divisions of the plane of the ecliptic. Astrologers have devised many systems of calculating these house divisions. In the case of the equal house system the ecliptic is divided into twelve equal houses of 30° each. The first house begins at the ascendant and the others are numbered counterclockwise from that point. The first six are therefore below the horizon, and the other six are above. The positions of these houses remains fixed relative to the native. The signs and planets all move through the twelve houses during the course of a day, and the planets move through the signs over the course of months or years.

To create a horoscope, an astrologer first has to ascertain the exact time and place of the subject's birth, or the initiation of an event. The local standard time (adjusting for any daylight saving time or war time) is then converted into Greenwich Mean Time or Universal Time at that same instant. The astrologer then has to convert this into the local sidereal time at birth in order to be able to calculate the ascendant and midheaven. The astrologer will next consult a set of tables called an ephemeris, which lists the location of the Sun, Moon and planets for a particular year, date and sidereal time, with respect to the northern hemisphere vernal equinox or the fixed stars (depending on which astrological system is being used). The astrologer then adds or subtracts the difference between the longitude of Greenwich and the longitude of the place in question to determine the true local mean time (LMT) at the place of birth to show where planets would be visible above the horizon at the precise time and place in question. Planets hidden from view beneath the earth are also shown in the horoscope.

The horoscope features 12 sectors around the circle of the ecliptic, starting from the eastern horizon with the ascendant or rising sign. These 12 sectors are called the houses and numerous systems for calculating these divisions exist. Tables of houses have been published since the 19th Century to make this otherwise demanding task easier.

The chart thus begins with a framework of 12 houses. Upon this the signs of the zodiac are superimposed. In the equal house system the cusp between any two houses will fall at the same degree for each of the at 12° of Leo, the second house will begin at 12° of Virgo, the third at 12° Libra, and so on. In house systems that take into consideration the effects of the angle of intersection between the planes of the horizon and the ecliptic, the calculations are more complicated. For these calculations it is essential to know the latitude of the event. Tables are available for these calculations, but they are now commonly calculated by computer. Most astrology computer programs allow the user to choose from a variety of house systems.

Having established the relative positions of the signs in the houses, the astrologer positions the sun, moon, and planets at their proper celestial longitudes. Some astrologers also take note of minor planetary bodies, fixed stars, asteroids (for example, Chiron) and other mathematically calculated points and angles such as the vertex, equatorial ascendant, etc. Many astrologers also use what are commonly referred to as Arabic parts (or Greek Lots), the most common of which is the Part of Fortune (Pars Fortunae).

To complete the horoscope the astrologer will consider the aspects or relative angles between pairs of planets. More exact aspects are considered more important. The difference between the exact aspect and the actual aspect is called the orb. Those generally recognized by the astrological community are Conjunction (0°), Opposition (180°), Square (90°), Trine (120°), Sextile (60°), Semi-Square (45°), Sesquisquare (135°), and Quincunx (150°). Understandably these aspects are more significant when they are exact, but they are considered to function within an orb of influence, the size of which varies according to the importance of each aspect. Thus conjunctions are believed to operate with a larger orb than sextiles. Most modern astrologers use an orb of 8° or less for aspects involving the Sun, Moon, and Jupiter and smaller orbs for the other points. Some astrologers, such as practitioners of Cosmobiology, and Uranian astrology, use minor aspects (15°, 22.5°, 67.5°, 72°, 75°, 105°, 112.5°, 157.5°, 165°) with much narrower orbs.

The ascendant (ASC) is a point on the ecliptic that rises on the eastern horizon at sunrise and changes as the earth rotates on its axis. The ascendant is very important in astrological chart interpretation. It exerts more power than the sun, moon and planets because it infiltrates everything in the natal chart. The ascendant is the first point of energy in the natal chart and it represents the way we view life. The sign on the ascendant characterises our expression of “who we are” when dealing with others, and our initial action when dealing with day-to-day concerns.Longitude is necessary in order to determine the position of the Ascendant because horoscopes use local time. Having constructed the horoscope, the astrologer can begin the task of interpreting the chart. This interpretation depends upon which branch of horoscopic astrology is being used......